Current advances in the use of bioluminescence assays for drug discovery: an update of the last ten years

INTRODUCTION

Bioluminescence is a well-established optical detection technique widely used in several bioanalytical applications, including high-throughput and high-content screenings. Thanks to advances in synthetic biology techniques and deep learning, a wide portfolio of luciferases is now available with tuned emission wavelengths, kinetics, and high stability. These luciferases can be implemented in the drug discovery and development pipeline, allowing high sensitivity and multiplexing capability.

AREAS COVERED

This review summarizes the latest advancements of bioluminescent systems as toolsets in drug discovery programs for in vitro applications. Particular attention is paid to the most advanced bioluminescence-based technologies for drug screening over the past 10 years (from 2013 to 2023) such as cell-free assays, cell-based assays based on genetically modified cells, bioluminescence resonance energy transfer, and protein complementation assays in 2D and 3D cell models.

EXPERT OPINION

The availability of tuned bioluminescent proteins with improved emission and stability properties is vital for the development of bioluminescence assays for drug discovery, spanning from reporter gene technology to protein-protein techniques. Further studies, combining machine learning with synthetic biology, will be necessary to obtain new tools for sustainable and highly predictive bioluminescent drug discovery platforms.

An easy method for quantification of anaerobic and microaerobic gene expression with fluorescent reporter proteins

Fluorescent proteins, such as green fluorescent proteins, are invaluable tools for detecting and quantifying gene expression in high-throughput reporter gene assays. However, they introduce significant inaccuracies in studies involving microaerobiosis or anaerobiosis, as oxygen is required for the maturation of these proteins' chromophores. In this study, the authors highlight the errors incurred by using fluorescent proteins under limited oxygenation by comparing standard fluorescence-based reporter gene assays to quantitative real-time PCR data in the study of a complex oxygen-regulated gene network. Furthermore, a solution to perform quantification of anaerobic and microaerobic gene expression with fluorescent reporter proteins using a microplate reader with an oxygen control system and applying pulses of full oxygenation before fluorescence measurements is provided.

Comprehensive Evaluation System for Post-Metabolic Activity of Potential Thyroid-Disrupting Chemicals

Endocrine-disrupting chemicals (EDCs) are compounds that disturb hormonal homeostasis by binding to receptors. EDCs are metabolized through hepatic enzymes, causing altered transcriptional activities of hormone receptors, and thus necessitating the exploration of the potential endocrine-disrupting activities of EDC-derived metabolites. Accordingly, we have developed an integrative workflow for evaluating the post-metabolic activity of potential hazardous compounds. The system facilitates the identification of metabolites that exert hormonal disruption through the integrative application of an MS/MS similarity network and predictive biotransformation based on known hepatic enzymatic reactions. As proof-of-concept, the transcriptional activities of 13 chemicals were evaluated by applying the in vitro metabolic module (S9 fraction). Identified among the tested chemicals were three thyroid hormone receptor (THR) agonistic compounds that showed increased transcriptional activities after phase I+II reactions (T3, 309.1 ± 17.3%; DITPA, 30.7 ± 1.8%; GC-1, 160.6 ± 8.6% to the corresponding parents). The metabolic profiles of these three compounds showed common biotransformation patterns, particularly in the phase II reactions (glucuronide conjugation, sulfation, GSH conjugation, and amino acid conjugation). Data-dependent exploration based on molecular network analysis of T3 profiles revealed that lipids and lipid-like molecules were the most enriched biotransformants. The subsequent subnetwork analysis proposed 14 additional features, including T4 in addition to 9 metabolized compounds that were annotated by prediction system based on possible hepatic enzymatic reaction. The other 10 THR agonistic negative compounds showed unique biotransformation patterns according to structural commonality, which corresponded to previous in vivo studies. Our evaluation system demonstrated highly predictive and accurate performance in determining the potential thyroid-disrupting activity of EDC-derived metabolites and for proposing novel biotransformants.

Establishment of an In Bacterio Assay for the Assessment of Carbon Storage Regulator A (CsrA) Inhibitors

Polymicrobial infections involving various combinations of microorganisms, such as Escherichia, Pseudomonas, or Yersinia, can lead to acute and chronic diseases in for example the gastrointestinal and respiratory tracts. Our aim is to modulate microbial communities by targeting the posttranscriptional regulator system called carbon storage regulator A (CsrA) (or also repressor of secondary metabolites (RsmA)). In previous studies, we identified easily accessible CsrA binding scaffolds and macrocyclic CsrA binding peptides through biophysical screening and phage display technology. However, due to the lack of an appropriate in bacterio assay to evaluate the cellular effects of these inhibitor hits, the focus of the present study is to establish an in bacterio assay capable of probing and quantifying the impact on CsrA-regulated cellular mechanisms. We have successfully developed an assay based on a luciferase reporter gene assay, which in combination with a qPCR expression gene assay, allows for the monitoring of expression levels of different downstream targets of CsrA. The chaperone protein CesT was used as a suitable positive control for the assay, and in time-dependent experiments, we observed a CesT-mediated increase in bioluminescence over time. By this means, the cellular on-target effects of non-bactericidal/non-bacteriostatic virulence modulating compounds targeting CsrA/RsmA can be evaluated.

Liquid Crystal Monomer: A Potential PPARγ Antagonist

Liquid crystal monomers (LCMs) are a large family of artificial ingredients that have been widely used in global liquid crystal display (LCD) industries. As a major constituent in LCDs as well as the end products of e-waste dismantling, LCMs are of growing research interest with regard to their environmental occurrences and biochemical consequences. Many studies have analyzed LCMs in multiple environmental matrices, yet limited research has investigated the toxic effects upon exposure to them. In this study, we combined in silico simulation and in vitro assay validation along with omics integration analysis to achieve a comprehensive toxicity elucidation as well as a systematic mechanism interpretation of LCMs for the first time. Briefly, the high-throughput virtual screen and reporter gene assay revealed that peroxisome proliferator-activated receptor gamma (PPARγ) was significantly antagonized by certain LCMs. Besides, LCMs induced global metabolome and transcriptome dysregulation in HK2 cells. Notably, fatty acid β-oxidation was conspicuously dysregulated, which might be mediated through multiple pathways (IL-17, TNF, and NF-kB), whereas the activation of AMPK and ligand-dependent PPARγ antagonism may play particularly important parts. This study illustrated LCMs as a potential PPARγ antagonist and explored their toxicological mode of action on the trans-omics level, which provided an insightful overview in future chemical risk assessment.

Development of a reporter gene assay for antibody dependent cellular cytotoxicity activity determination of anti-rabies virus glycoprotein antibodies

Rabies is a viral disease that is nearly 100% fatal once clinical signs and symptoms develop. Post-exposure prophylaxis can efficiently prevent rabies, and antibody (Ab) induction by vaccination or passive immunization of human rabies immunoglobulin (HRIG) or monoclonal antibodies (mAbs) play an integral role in prevention against rabies. In addition to their capacity to neutralize viruses, antibodies exert their antiviral effects by antibody-dependent cellular cytotoxicity (ADCC), which plays an important role in antiviral immunity and clearance of viral infections. For antibodies against rabies virus (RABV), evaluation of ADCC activity was neglected. Here, we developed a robust cell-based reporter gene assay (RGA) for the determination of the ADCC activity of anti-RABV antibodies using CVS-N2c-293 cells, which stably express the glycoprotein (G) of RABV strain CVS-N2c as target cells, and Jurkat cells, which stably express FcγRⅢa and nuclear factor of activated T cells (NFAT) reporter gene as effector cells (Jurkat/NFAT-luc/FcγRⅢa cells). The experimental parameters were carefully optimized, and the established ADCC assay was systematically validated according to the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q2 guideline. We also evaluated the ADCC activity of anti-RABV antibodies, including mAbs, HRIG, and vaccine induced antisera, and found that all test antibodies exhibited ADCC activity with varied strengths. The established RGA provides a novel method for evaluating the ADCC of anti-RABV antibodies.

A novel GJA5 variant associated with increased risk of essential hypertension

OBJECTIVES

Gap junction protein alpha 5 (GJA5), also termed connexin 40 (Cx40), exerts a pivotal role in the mediation of vascular wall tone and two closely-linked polymorphisms in the GJA5 promoter (-44G>A and +71A>G) have been associated with enhanced susceptibility to essential hypertension (EH) in men. The present investigation aimed to ascertain whether a novel common polymorphism within the upstream regulatory region of GJA5 (transcript 1B), -26A>G (rs10465885), confers an increased risk of EH.

METHODS

For this investigation, 380 unrelated patients with EH and 396 unrelated normotensive individuals employed as control persons were enrolled from the Chinese Han-ethnicity population, and their GJA5 genotypes and plasma renin concentrations were determined by Sanger sequencing and an automated chemiluminescent immunoassay, respectively. The functional effect of the GJA5 variant was explored in cultured murine cardiomyocytes by dual-light reporter gene analysis.

RESULTS

The GJA5 variant conferred a significantly increased risk for EH (OR: 2.156; 95% CL: 1.661-2.797, P < 0.0001), and significantly increased plasma renin levels were measured in patients with EH in comparison with control individuals (46.3±7.2 vs 37.4±6.9, P < 0.0001). A promoter-luciferase analysis revealed significantly diminished activity of the promoter harboring the minor allele for this variation in comparison with its wild-type counterpart (165.67±16.85 vs 61.53±8.67, P = 0.0007).

CONCLUSIONS

These findings indicate that the novel variant upstream of the GJA5 gene (-26A>G) confers a significantly increased vulnerability of EH in humans, suggesting potential clinical implications for precisive prophylaxis and treatment of EH.

Improving Reporter Gene Assay Methodology for Evaluating the Ability of Compounds to Restore P53 Activity

Tumor suppressor protein P53 induces cycle arrest and apoptosis by mediating the transcriptional expression of its target genes. Mutations causing conformational abnormalities and post-translational modifications that promote degradation are the main reasons for the loss of P53 function in tumor cells. Reporter gene assays that can scientifically reflect the biological function can help discover the mechanism and therapeutic strategies that restore P53 function. In the reporter gene system of this work, tetracycline-inducible expression of wild-type P53 was used to provide a fully activated state as a 100% activity reference for the objective measurement of biological function. It was confirmed by RT-qPCR, cell viability assay, immunofluorescence, and Western blot analysis that the above-mentioned reporter gene system could correctly reflect the differences in biological activity between the wild-type and mutants. After that, the system was tentatively used for related mechanism research and compound activity evaluation. Through the tetracycline-induced co-expression of wild-type P53 and mutant P53 in exact proportion, it was observed that the response modes of typical transcriptional response elements (TREs) to dominant negative P53 mutation effect were not exactly the same. Compared to the relative multiple-to-solvent control, the activity percentage relative to the 100% activity reference of wild-type P53 can better reflect the actual influence of the so-called P53 mutant reactivator. Similarly, relative to the 100% activity reference, it can objectively reflect the biological effects caused by the inhibitor of P53 negative factors, such as MDM2. In conclusion, this study provides a 100% activity reference and a reliable calculation model for relevant basic research and drug development.

A luciferase reporter assay for ecdysone agonists using HEK293T cells

Ecdysone agonists are a class of insecticides that activate the ecdysone receptor (EcR) heterodimerized with the ultraspiracle (USP). Here, we report a new luciferase reporter assay for ecdysone agonists. The assay employs mammalian HEK293T cells transiently transfected with the EcR and USP genes of Chilo suppressalis, along with the taiman (Tai) gene of Drosophila melanogaster that encodes a steroid receptor coactivator. This assay system gave results consistent with those of radioligand binding assays and showed sensitivity superior to that of the existing in vitro methods. In addition, use of the heterologous host cells precludes perturbation from intrinsic players of the ecdysone signaling, which is a potential drawback of insect cell-based methods. This reporter system is suitable for detailed structure-activity analysis of ecdysone agonists and will serve as a valuable tool for the rational design of novel insect growth regulators.

Identification of SOX18 as a New Gene Predisposing to Congenital Heart Disease

Congenital heart disease (CHD) is the most frequent kind of birth deformity in human beings and the leading cause of neonatal mortality worldwide. Although genetic etiologies encompassing aneuploidy, copy number variations, and mutations in over 100 genes have been uncovered to be involved in the pathogenesis of CHD, the genetic components predisposing to CHD in most cases remain unclear. We recruited a family with CHD from the Chinese Han population in the present investigation. Through whole-exome sequencing analysis of selected family members, a new SOX18 variation, namely NM_018419.3:c.349A>T; p.(Lys117*), was identified and confirmed to co-segregate with the CHD phenotype in the entire family by Sanger sequencing analysis. The heterozygous variant was absent from the 384 healthy volunteers enlisted as control individuals. Functional exploration via luciferase reporter analysis in cultivated HeLa cells revealed that Lys117*-mutant SOX18 lost transactivation on its target genes NR2F2 and GATA4, two genes responsible for CHD. Moreover, the genetic variation terminated the synergistic activation between SOX18 and NKX2.5, another gene accountable for CHD. The findings strongly indicate SOX18 as a novel gene contributing to CHD, which helps address challenges in the clinical genetic diagnosis and prenatal prophylaxis of CHD.

Two-color fluorescent proteins reporting survivin regulation in breast cancer cells for high throughput drug screening

Reporter gene assay is widely used for high throughput drug screening and drug action mechanism evaluation. In this study, we developed a robust dual-fluorescent reporter assay to detect drugs repressing the transcription of survivin, a cancer biomarker from the inhibitor of apoptosis family, in breast cancer cells cultured in three-dimensional (3D) microbioreactors. Survivin is overexpressed in numerous malignancies but almost silent in normal tissue cells and is considered a lead target for cancer therapy. Breast cancer MCF-7 cells were engineered to express enhanced green fluorescent protein driven by a survivin promoter and red fluorescent protein driven by a cytomegalovirus promoter as internal control to detect changes in survivin expression in cells as affected by drugs. This 3D dual-fluorescent reporter assay was validated with YM155 and doxorubicin, which were known to downregulate survivin in cancer cells, and further evaluated with two widely used anticancer compounds, cisplatin, and epigallocatechin gallate, to evaluate their effects on survivin expression. The results showed that the 3D dual-fluorescent reporter assay was robust for high throughput screening of drugs targeting survivin in breast cancer cells.

PRRX1 Loss-of-Function Mutations Underlying Familial Atrial Fibrillation

Background

Atrial fibrillation (AF) is the most common form of clinical cardiac dysrhythmia responsible for thromboembolic cerebral stroke, congestive heart failure, and death. Aggregating evidence highlights the strong genetic basis of AF. Nevertheless, AF is of pronounced genetic heterogeneity, and in an overwhelming majority of patients, the genetic determinants underpinning AF remain elusive.

Methods and Results

By genome‐wide screening with polymorphic microsatellite markers and linkage analysis in a 4‐generation Chinese family affected with autosomal‐dominant AF, a novel locus for AF was mapped to chromosome 1q24.2–q25.1, a 3.20‐cM (≈4.19 Mbp) interval between markers D1S2851 and D1S218, with the greatest 2‐point logarithm of odds score of 4.8165 for the marker D1S452 at recombination fraction=0.00. Whole‐exome sequencing and bioinformatics analyses showed that within the mapping region, only the mutation in the paired related homeobox 1 (PRRX1) gene, NM_022716.4:c.319C>T;(p.Gln107*), cosegregated with AF in the family. In addition, sequencing analyses of PRRX1 in another cohort of 225 unrelated patients with AF revealed a new mutation, NM_022716.4:c.437G>T; (p.Arg146Ile), in a patient. The 2 mutations were absent in 908 control subjects. Biological analyses in HeLa cells demonstrated that the 2 mutants had significantly diminished transactivation on the target genes ISL1 and SHOX2 and markedly decreased ability to bind the promoters of ISL1 and SHOX2 (2 genes causally linked to AF), although with normal intracellular distribution.

Conclusions

This study first indicates that PRRX1 loss‐of‐function mutations predispose to AF, which provides novel insight into the molecular pathogenesis underpinning AF, implying potential implications for precisive prophylaxis and management of AF.

Substituted Two- to Five-Ring Polycyclic Aromatic Compounds Are Potent Agonists of Atlantic Cod (Gadus morhua) Aryl Hydrocarbon Receptors Ahr1a and Ahr2a

Polycyclic aromatic hydrocarbons (PAHs) are among the most toxic and bioavailable components found in petroleum and represent a high risk to aquatic organisms. The aryl hydrocarbon receptor (Ahr) is a ligand-activated transcription factor that mediates the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other planar aromatic hydrocarbons, including certain PAHs. Ahr acts as a xenosensor and modulates the transcription of biotransformation genes in vertebrates, such as cytochrome P450 1A (cyp1a). Atlantic cod (Gadus morhua) possesses two Ahr proteins, Ahr1a and Ahr2a, which diverge in their primary structure, tissue-specific expression, ligand affinities, and transactivation profiles. Here, a luciferase reporter gene assay was used to assess the sensitivity of the Atlantic cod Ahrs to 31 polycyclic aromatic compounds (PACs), including two- to five-ring native PAHs, a sulfur-containing heterocyclic PAC, as well as several methylated, methoxylated, and hydroxylated congeners. Notably, most parent compounds, including naphthalene, phenanthrene, and partly, chrysene, did not act as agonists for the Ahrs, while hydroxylated and/or alkylated versions of these PAHs were potent agonists. Importantly, the greater potencies of substituted PAH derivatives and their ubiquitous occurrence in nature emphasize that more knowledge on the toxicity of these environmentally and toxicologically relevant compounds is imperative.

Development of a reporter gene method to measure the bioactivity of anti-CD38 × CD3 bispecific antibody

Background

A T cell-redirecting bispecific antibody (bsAb) consisting of a tumor-binding unit and a T cell-binding unit is a large group of antibody-based biologics against death-causing cancer diseases. The anti-CD38 × anti-CD3 bsAb (Y150) is potential for treating multiple myeloma (MM). When developing a cell-based reporter gene bioassay to assess the activities of Y150, it was found that the expression of CD38 on the human T lymphocyte cells (Jurkat) caused the nonspecific activation, which interfered with the specific T cells activation of mediated by the Y150 and CD38(+) tumor cells.

Methods

Here, we first knocked-out the CD38 expression on Jurkat T cell line by CRISPR-Cas9 technology, then developed a stable monoclonal CD38(−) Jurkat T cell line with an NFAT-RE driving luciferase expressing system. Further based on the CD38(−) Jurkat cell, we developed a reporter gene method to assess the bioactivity of the anti-CD38 × anti-CD3 bsAb.

Results

Knocking out CD38 expression abolished the nonspecific self-activation of the Jurkat cells. The selected stable monoclonal CD38(−) Jurkat T cell line assured the robustness of the report genes assay for the anti-CD38 × anti-CD3 bsAb. The relative potencies of the Y150 measured by the developed reporter gene assay were correlated with those by the flow-cytometry-based cell cytotoxicity assay and by the ELISA-based binding assay.

Conclusions

The developed reporter gene assay was mechanism of action-reflective for the bioactivity of anti-CD38 × anti-CD3 antibody, and suitable for the quality control for the bsAb product.

Reporter gene assays for screening and identification of novel molting hormone- and juvenile hormone-like chemicals

A reporter gene assay (RGA) is used to investigate the activity of synthetic chemicals mimicking the molting hormones (MHs) and juvenile hormones (JHs) of insects, so-called insect growth regulators (IGRs). The MH receptor, a heterodimer of the ecdysone receptor (EcR) and ultraspiracle (USP), and the JH receptor Methoprene-tolerant (Met) are ligand-dependent transcription factors. Ligand-bound EcR-USP and Met bind to specific cis-acting DNA elements, referred to as the ecdysone-responsive element (EcRE) and the JH-responsive element (JHRE), respectively, in order to transactivate target genes. Insect hormone-induced transactivation systems have been reconstituted by the introduction of reporter genes under the control of EcRE and JHRE, or two-hybrid reporter genes, into insect, mammalian, and yeast cells expressing receptor proteins. RGA is easy to use and convenient for examining the MH- and JH-like activities of synthetic chemicals and is suitable for the high-throughput screening of novel structural classes of chemicals targeting EcR-USP and Met.

Development of a robust reporter gene assay for measuring the bioactivity of OX40-targeted therapeutic antibodies

OX40 plays a prominent role in the onset and development of solid tumors, and OX40-targeted monoclonal antibodies (mAbs) have entered clinical trials for various tumors. Bioactivity determination of therapeutic mAbs is of great significance in product quality, however, mechanism of action-based bioassays to determine the bioactivity of anti-OX40 mAbs is still lacking. Here, we established a reporter gene assay system based on two cell lines, namely Jurkat-OX40-NFκB-Luc which stably expresses NFκB-controlled luciferase, and Raji cells which inherently express FcγRs. In the model, FcγRs on Raji cells could crosslink the Fc of anti-OX40 mAbs, which leads to the further crosslinking between Fab of anti-OX40 mAbs and OX40 on Jurkat-OX40-NFκB-Luc cells. OX40 crosslinking could activate Jurkat-OX40-NFκB-Luc cells, and induce the expression of NFκB-controlled luciferase, the extent of which could reflect the bioactivity of anti-OX40 mAbs in a dose-dependent manner. After the optimization of various assay conditions, the validation of the cell-based bioassay showed good assay performance characteristics, including specificity, accuracy, precision, linearity, and stability. This innovative assay that is based on the OX40-NFκB pathway can be a powerful pool to measure the bioactivity of OX40-targeted mAbs.

Polymorphisms of KLF3 gene coding region and identification of their functionality for abdominal fat in chickens

KLF3 is a member of the Kruppel‐like factor (KLF) family of transcription factors, and plays an important role in several biological processes, including adipogenesis, erythropoiesis and B‐cell development. The purposes of this study are to search for polymorphisms of KLF3 coding region and to provide functional evidence for abdominal fat in chickens. A total of 168 SNPs in KLF3 coding region were detected in a unique chicken population, the Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF). Of which three single nucleotide polymorphisms (g.3452T > C, g.8663A > G and g.10751G > A) were significantly correlated with abdominal fat weight (AFW) and abdominal fat percentage (AFP) of 329 birds from the 19th generation of NEAUHLF (FDR < 0.05). The reporter gene assay was performed to verify functionality of these three SNPs in both ICP‐1 and DF1 cells. Results showed that the luciferase activity of G allele was significantly higher than that of A allele in g.10751G > A (p < 0.05). However, there were no significant differences between different alleles of others two SNPs in luciferase activity. Overall, KLF3 is an important candidate gene that affects chicken abdominal fat content, and the g.10751G > A is a functional variant that potential would be applied to marker‐assisted selection (MAS) for selective breeding programme.

Quantification of Bevacizumab Activity Following Treatment of Patients With Ovarian Cancer or Glioblastoma

Highly sensitive reporter-gene assays have been developed that allow both the direct vascular endothelial growth factor (VEGF) neutralizing activity of bevacizumab and the ability of bevacizumab to activate antibody dependent cellular cytotoxicity (ADCC) to be quantified rapidly and in a highly specific manner. The use of these assays has shown that in 46 patients with ovarian cancer following four cycle of bevacizumab treatment, and in longitudinal samples from the two patients that respond to bevacizumab therapy from a small cohort of patients with glioblastoma, that there is a reasonably good correlation between bevacizumab drug levels determined by ELISA and bevacizumab activity, determined using either the VEGF-responsive reporter gene, or the ADCC assays. One of the two primary non-responders with glioblastoma exhibited high levels of ADCC activity suggesting reduced bevacizumab Fc engagement in vivo in contrast to the other primary non-responder, and the two secondary non-responders with a decreasing bevacizumab PK profile, determined by ELISA that exhibited low to undetectable ADCC activity. Drug levels were consistently higher than bevacizumab activity determined using the reporter gene assay in serial samples from one of the secondary non-responders and lower in some samples from the other secondary non-responder and ADCC activity was markedly lower in all samples from these patients suggesting that bevacizumab activity may be partially neutralized by anti-drug neutralizing antibodies (NAbs). These results suggest that ADCC activity may be correlated with the ability of some patients to respond to treatment with bevacizumab while the use of the VEGF-responsive reporter-gene assay may allow the appearance of anti-bevacizumab NAbs to be used as a surrogate maker of treatment failure prior to the clinical signs of disease progression.

A reporter gene assay for measuring the bioactivity of anti-LAG-3 therapeutic antibodies

Although enormous success has been achieved with anti-PD-1/PD-L1 and anti-CTLA-4 monoclonal antibodies (mAbs), their unsatisfactory response rate in cancer patients has been driving the research and development of novel immune checkpoint inhibitors (ICIs). Anti-LAG-3 mAbs, as one of the most promising candidates, are now being tested for various human cancers at different stages of clinical trials. Here, we describe the development and validation of a reporter gene assay (RGA) to measure the bioactivity of anti-LAG-3 mAbs. We established the bioassay based on parental Raji cells and a Jurkat cell line stably transfected with human LAG-3 gene and luciferase reporter elements controlled by nuclear factor of activated T cell (NFAT) from the IL-2 promoter. After optimization of key parameters, the established RGA showed excellent precision, specificity, accuracy, and stability. The mechanism of action (MOA) relatedness and the excellent assay performance make the RGA suitable for the characterization, lot release, and stability test of anti-LAG-3 mAbs.

Discovery of Eicosapentaenoic Acid Esters of Hydroxy Fatty Acids as Potent Nrf2 Activators

Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are a recently discovered class of biologically active lipids with anti-inflammatory and anti-diabetic properties. Despite the possible link between endogenous FAHFA levels and nuclear factor erythroid 2-related factor 2 (Nrf2), their possible function as antioxidants and the mechanisms involved in this are unknown. Here, we investigate FAHFAs’ plausible antioxidant potential with reference to their effect on the Nrf2 levels, oxidative stress, and lipid droplet oxidation in human hepatocytes (C3A). Six authentic FAHFAs were chemically synthesized and performed activity-based screening by reporter gene assay. Among them, eicosapentaenoic acid (EPA) esterified 12-hydroxy stearic acid (12-HSA) and 12-hydroxy oleic acid (12-HOA) FAHFAs showed less cytotoxicity compared to their free fatty acids and potent activators of Nrf2. To define their mode of action, relative levels of nuclear Nrf2 were determined, which found a higher amount of Nrf2 in nucleus of cells treated with 12-EPAHSA compared to the control. Furthermore, 12-EPAHSA increased the expression of Nrf2-dependent antioxidant enzyme genes (NQO1, GCLM, GCLC, SOD-1, and HO-1). Fluorescence imaging analysis of linoleic-acid-induced lipid droplets (LDs) in C3A cells treated with 12-EPAHSA revealed the strong inhibition of small-size LD oxidation. These results suggest that EPA-derived FAHFAs as a new class of lipids with less cytotoxicity, and strong Nrf2 activators with plausible antioxidant effects via the induction of cytoprotective proteins against oxidative stress, induced cellular damage.

The canonical non-homologous end joining factor XLF promotes chromosomal deletion rearrangements in human cells

Clastogen exposure can result in chromosomal rearrangements, including large deletions and inversions that are associated with cancer development. To examine such rearrangements in human cells, here we developed a reporter assay based on endogenous genes on chromosome 12. Using the RNA-guided nuclease Cas9, we induced two DNA double-strand breaks, one each in the GAPDH and CD4 genes, that caused a deletion rearrangement leading to CD4 expression from the GAPDH promoter. We observed that this GAPDH-CD4 deletion rearrangement activates CD4+ cells that can be readily detected by flow cytometry. Similarly, double-strand breaks in the LPCAT3 and CD4 genes induced an LPCAT3-CD4 inversion rearrangement resulting in CD4 expression. Studying the GAPDH-CD4 deletion rearrangement in multiple cell lines, we found that the canonical non-homologous end joining (C-NHEJ) factor XLF promotes these rearrangements. Junction analysis uncovered that the relative contribution of C-NHEJ appears lower in U2OS than in HEK293 and A549 cells. Furthermore, an ATM kinase inhibitor increased C-NHEJ-mediated rearrangements only in U2OS cells. We also found that an XLF residue that is critical for an interaction with the C-NHEJ factor X-ray repair cross-complementing 4 (XRCC4), and XRCC4 itself are each important for promoting both this deletion rearrangement and end joining without insertion/deletion mutations. In summary, a reporter assay based on endogenous genes on chromosome 12 reveals that XLF-dependent C-NHEJ promotes deletion rearrangements in human cells and that cell type-specific differences in the contribution of C-NHEJ and ATM kinase inhibition influence these rearrangements.

Compound Identification Using Liquid Chromatography and High-Resolution Noncontact Fraction Collection with a Solenoid Valve

We describe the development of a high-resolution, noncontact fraction collector for liquid chromatography (LC) separations, allowing high-resolution fractionation in high-density well plates. The device is based on a low-dead-volume solenoid valve operated at 1–30 Hz for accurate collection of fractions of equal volume. The solenoid valve was implemented in a modified autosampler resulting in the so-called FractioMate fractionator. The influence of the solenoid supply voltage on solvent release was determined and the effect of the frequency, flow rate, and mobile phase composition was studied. For this purpose, droplet release was visually assessed for a wide range of frequencies and flow rates, followed by quantitative evaluation of a selection of promising settings for highly accurate, repeatable, and stable fraction collection. The potential of the new fraction collector for LC-based bioactivity screening was demonstrated by fractionating the LC eluent of a mixture of estrogenic and androgenic compounds, and a surface water sample (blank and spiked with bioactives) combining mass spectrometric detection and two reporter gene assays for bioactivity detection of the fractions. Additionally, a mixture of two compounds was repeatedly LC separated and fractionated to assess the feasibility of the system for analyte isolation followed by nuclear magnetic resonance analysis.

A Cell-Based Strategy for Bioactivity Determination of Long-Acting Fc-Fusion Recombinant Human Growth Hormone

The long-acting growth hormone (LAGH) is a promising alternative biopharmaceutical to treat growth hormone (GH) deficiency in children, and it was developed using a variety of technologies by several pharmaceutical companies. Most LAGH preparations, such as Fc fusion protein, are currently undergoing preclinical study and clinical trials. Accurate determination of bioactivity is critical for the efficacy of quality control systems of LAGH. The current in vivo rat weight gain assays used to determine the bioactivity of recombinant human GH (rhGH) in pharmacopoeias are time-consuming, expensive, and imprecise, and there are no recommended bioassays for LAGH bioactivity in pharmacopoeias. Therefore, we developed a cell-based bioassay for bioactivity determination of therapeutic long-acting Fc-fusion recombinant human growth hormone (rhGH-Fc) based on the luciferase reporter gene system, which is involved in the full-length human GH receptor (hGHR) and the SG (SIE and GAS) response element. The established bioassay was comprehensively validated according to the International Council for Harmonization (ICH) Q2 (R1) guidelines and the Chinese Pharmacopoeia, and is highly precise, time-saving, simple, and robust. The validated bioassay could be qualified for bioactivity determination during the research, development, and manufacture of rhGH-Fc, and other LAGH formulations.

Nanoluciferase Reporter Gene System Directed by Tandemly Repeated Pseudo-Palindromic NFAT-Response Elements Facilitates Analysis of Biological Endpoint Effects of Cellular Ca2+ Mobilization

NFAT is a cytoplasm-localized hyper-phosphorylated transcription factor that is activated through dephosphorylation by calcineurin, a Ca²⁺/calmodulin-dependent phosphatase. A non-palindromic NFAT-response element (RE) found in the IL2 promoter region has been commonly used for a Ca²⁺-response reporter gene system, but requirement of concomitant activation of AP-1 (Fos/Jun) often complicates the interpretation of obtained results. A new nanoluciferase (NanoLuc) reporter gene containing nine-tandem repeats of a pseudo-palindromic NFAT-RE located upstream of the IL8 promoter was designed to monitor Ca²⁺-induced transactivation activity of NFAT in human embryonic kidney (HEK) 293 cells by measuring luciferase activities of NanoLuc and co-expressed firefly luciferase for normalization. Ionomycin treatment enhanced the relative luciferase activity (RLA), which was suppressed by calcineurin inhibitors. HEK293 cells that stably express human STIM1 and Orai1, components of the store-operated calcium entry (SOCE) machinery, gave a much higher RLA by stimulation with thapsigargin, an inhibitor of sarcoplasmic/endoplamic reticulum Ca²⁺-ATPase (SERCA). HEK293 cells deficient in a penta-EF-hand Ca²⁺-binding protein ALG-2 showed a higher RLA value than the parental cells by stimulation with an acetylcholine receptor agonist carbachol. The novel reporter gene system is found to be useful for applications to cell signaling research to monitor biological endpoint effects of cellular Ca²⁺ mobilization.

TBX1 loss-of-function mutation contributes to congenital conotruncal defects

Conotruncal defects (CTDs) account for ~30% of all types of congenital heart disease and contribute to increased morbidity and mortality rates. Increasing evidence suggests that genetic risk factors are involved in the pathogenesis of CTDs. Mutations in a number of genes, including the TBX1 gene that codes for a T-box transcription factor essential for normal cardiovascular development, may contribute to the development of CTD. CTDs are genetically heterogeneous and the genetic defects responsible for CTDs in the majority of patients remain unknown. The present study sequenced the coding regions and splicing junction boundaries of TBX1 in 136 patients with CTDs and 300 matched healthy individuals. The disease-causing potential of the identified TBX1 sequence variation was evaluated using MutationTaster, PolyPhen-2, SIFT and PROVEN software. The functional characteristics of the mutant TBX1 gene were defined using a dual-luciferase reporter assay system. A novel heterozygous TBX1 mutation, p.S233Y, was identified in a patient with transposition of the great arteries (TGA) and a ventricular septal defect. This mutation was absent in the 300 controls and altered the amino acid produced, serine, which is evolutionarily conserved across several species, and was predicted to be pathogenic in silico. Luciferase assays conducted in COS-7 cells demonstrated that the newly identified TBX1 mutation was associated with significantly diminished transcriptional activation of the ANF promoter compared with the wild-type TBX1. To the best of our knowledge, the present study is the first to associate a TBX1 loss-of-function mutation with enhanced susceptibility to TGA, which adds significant insight to the molecular mechanism of TGA.

Specificity of presenilin-1- and presenilin-2-dependent γ-secretases towards substrate processing

The two presenilin‐1 (PS1) and presenilin‐2 (PS2) homologs are the catalytic core of the γ‐secretase complex, which has a major role in cell fate decision and Alzheimer's disease (AD) progression. Understanding the precise contribution of PS1‐ and PS2‐dependent γ‐secretases to the production of β‐amyloid peptide (Aβ) from amyloid precursor protein (APP) remains an important challenge to design molecules efficiently modulating Aβ release without affecting the processing of other γ‐secretase substrates. To that end, we studied PS1‐ and PS2‐dependent substrate processing in murine cells lacking presenilins (PSs) (PS1KO, PS2KO or PS1‐PS2 double‐KO noted PSdKO) or stably re‐expressing human PS1 or PS2 in an endogenous PS‐null (PSdKO) background. We characterized the processing of APP and Notch on both endogenous and exogenous substrates, and we investigated the effect of pharmacological inhibitors targeting the PSs activity (DAPT and L‐685,458). We found that murine PS1 γ‐secretase plays a predominant role in APP and Notch processing when compared to murine PS2 γ‐secretase. The inhibitors blocked more efficiently murine PS2‐ than murine PS1‐dependent processing. Human PSs, especially human PS1, expression in a PS‐null background efficiently restored APP and Notch processing. Strikingly, and contrary to the results obtained on murine PSs, pharmacological inhibitors appear to preferentially target human PS1‐ than human PS2‐dependent γ‐secretase activity.

Editor's Highlight: Development of Novel Neural Embryonic Stem CellTests for High-Throughput Screening of Embryotoxic Chemicals

There is a great demand for appropriate alternative methods to rapidly evaluate the developmental and reproductive toxicity of a wide variety of chemicals. We used the differentiation of mouse embryonic stem cells (mESCs) into cardiomyocytes as a basis for establishing a rapid and highly reproducible invitro embryotoxicity test known as the Hand1-Luc Embryonic Stem Cell Test (Hand1-Luc EST). In this study, we developed novel neural-Luc ESTs using two marker genes for neural development, tubulin beta-3 (Tubb3) and Reelin (Reln), and evaluated the capacity of these tests to predict developmental toxicity. In addition, we tested whether an integrated approach (a combination of neural-Luc ESTs and the Hand1-Luc EST) improved developmental toxicant detection. To perform our neural-Luc ESTs, we needed to generate stable transgenic mESCs with individual promoters linked to the luciferase gene, and to establish that similar changes in promoter activities and mRNA expression levels occur during neural differentiation. Based on the concentration-response curves of 15 developmental toxicants and 17 non-developmental toxic chemicals, we derived a prediction formula and assessed the capacity of this formula to predict developmental toxicity. Although both were highly sensitive and specific for predicting developmental toxicity, neural-Luc ESTs had similar predictive capacities. In contrast, neural-Luc ESTs and Hand1-Luc EST had significantly different predictive powers. As expected, the combination of these ESTs increased the sensitivity of developmental toxicant detection. These results demonstrate the convenience and the usefulness of this combination of ESTs as an alternative assay system for future toxicological and mechanistic studies of developmental toxicity.

Endoplasmic Reticulum Stress Induction and ERK1/2 Activation Contribute to Nefazodone-Induced Toxicity in Hepatic Cells

Nefazodone, an antagonist for the 5-hydroxytryptanine receptor, has been used for the treatment of depression. Acute liver injury has been documented to be associated with the use of nefazodone; however, the mechanisms of nefazodone-induced liver toxicity are not well defined. In this report, using biochemical and molecular analyses, we characterized the molecular mechanisms underlying the hepatotoxicity of nefazodone. We found that nefazodone induced endoplasmic reticulum (ER) stress in HepG2 cells, as the expression of typical ER stress markers, including CHOP, ATF-4, and p-eIF2α, was significantly increased, and splicing of XBP1 was observed. Nefazodone-suppressed protein secretion was evaluated using a Gaussia luciferase reporter assay that measures ER stress. The ER stress inhibitors (4-phenylbutyrate and salubrinal) and knockdown of ATF-4 gene attenuated nefazodone-induced ER stress and cytotoxicity. Nefazodone activated the MAPK signaling pathway, as indicated by increased phosphorylation of JNK, ERK1/2, and p38. Inhibition of ERK1/2 reduced ER stress caused by nefazodone. Taken together, our findings suggest that ER stress contributes to nefazodone-induced toxicity in HepG2 cells and that the MAPK signaling pathway plays an important role in ER stress.

A HAND2 Loss-of-Function Mutation Causes Familial Ventricular Septal Defect and Pulmonary Stenosis

Congenital heart disease (CHD) is the most common developmental abnormality, and is the leading noninfectious cause of mortality in neonates. Increasing evidence demonstrates that genetic defects play an important role in the pathogenesis of CHD. However, CHD exhibits substantial heterogeneity, and the genetic determinants for CHD remain unknown in the overwhelming majority of cases. In the current study, the coding exons and flanking introns of the HAND2 gene, which encodes a basic helix-loop-helix transcription factor essential for normal cardiovascular development, were sequenced in 192 unrelated patients with CHD, and a novel heterozygous mutation, p.S65I, was identified in a patient with congenital ventricular septal defect (VSD). Genetic analysis of the index patient’s pedigree revealed that the mutation was present in all seven affected family members available, but absent in the 13 unaffected family members examined. Besides, in addition to VSD, five of the proband’s close relatives also had pulmonary stenosis (PS), and the proband’s son also had double outlet right ventricle (DORV). The missense mutation, which altered an evolutionarily conserved amino acid, was absent in 300 unrelated, ethnically matched healthy individuals. Biological analyses using a dual-luciferase reporter assay system showed that the mutant HAND2 was associated with significantly diminished transcriptional activity. Furthermore, the mutation abolished the synergistic activation between HAND2 and GATA4, as well as NKX2.5—two other cardiac core transcriptional factors that have been causally linked to CHD. These findings indicate that HAND2 loss-of-function mutation contributes to human CHD, perhaps via its interaction with GATA4 and NKX2.5.

Detection of Aryl Hydrocarbon Receptor Activation by Some Chemicals in Food Using a Reporter Gene Assay

The purpose of this study was to examine whether a simple bioassay used for the detection of dioxins (DXNs) could be applied to detect trace amounts of harmful DXN-like substances in food products. To identify substances with possible DXN-like activity, we assessed the ability of various compounds in the environment to bind the aryl hydrocarbon receptor (AhR) that binds specifically to DXNs. The compounds tested included 19 polycyclic aromatic hydrocarbons (PAHs), 20 PAH derivatives (nitrated, halogenated, and aminated derivatives), 23 pesticides, six amino acids, and eight amino acid metabolites. The AhR binding activities (AhR activity) of these compounds were measured using the chemical activated luciferase gene expression (CALUX) reporter gene assay system. The majority of the PAHs exhibited marked AhR activity that increased in a concentration-dependent manner. Furthermore, there was a positive link between AhR activity and the number of aromatic rings in the PAH derivatives. Conversely, there appeared to be a negative correlation between AhR activity and the number of chlorine residues present on halogenated PAH derivatives. However, there was no correlation between AhR activity and the number and position of substituents among nitrated and aminated derivatives. Among the pesticides tested, the indole-type compounds carbendazim and thiabendazole showed high levels of activity. Similarly, the indole compound tryptamine was the only amino acid metabolite to induce AhR activity. The results are useful in understanding the identification and characterization of AhR ligands in the CALUX assay.

Luminol-based chemiluminescent signals: clinical and non-clinical application and future uses

Chemiluminescence (CL) is an important method for quantification and analysis of various macromolecules. A wide range of CL agents such as luminol, hydrogen peroxide, fluorescein, dioxetanes and derivatives of oxalate, and acridinium dyes are used according to their biological specificity and utility. This review describes the application of luminol chemiluminescence (LCL) in forensic, biomedical, and clinical sciences. LCL is a very useful detection method due to its selectivity, simplicity, low cost, and high sensitivity. LCL has a dynamic range of applications, including quantification and detection of macro and micromolecules such as proteins, carbohydrates, DNA, and RNA. Luminol-based methods are used in environmental monitoring as biosensors, in the pharmaceutical industry for cellular localization and as biological tracers, and in reporter gene-based assays and several other immunoassays. Here, we also provide information about different compounds that may enhance or inhibit the LCL along with the effect of pH and concentration on LCL. This review covers most of the significant information related to the applications of luminol in different fields.

Luciferase reporter assay in Drosophila and mammalian tissue culture cells

Luciferase reporter gene assays are one of the most common methods for monitoring gene activity. Because of their sensitivity, dynamic range, and lack of endogenous activity, luciferase assays have been particularly useful for functional genomics in cell-based assays, such as RNAi screening. This unit describes delivery of two luciferase reporters with other nucleic acids (siRNA/dsRNA), measurement of the dual luciferase activities, and analysis of data generated. The systematic query of gene function (RNAi) combined with the advances in luminescent technology have made it possible to design powerful whole genome screens to address diverse and significant biological questions.

Identification of thyroid hormone receptor active compounds using a quantitative high-throughput screening platform

To adapt the use of GH3.TRE-Luc reporter gene cell line for a quantitative high-throughput screening (qHTS) platform, we miniaturized the reporter gene assay to a 1536-well plate format. 1280 chemicals from the Library of Pharmacologically Active Compounds (LOPAC) and the National Toxicology Program (NTP) 1408 compound collection were analyzed to identify potential thyroid hormone receptor (TR) agonists and antagonists. Of the 2688 compounds tested, eight scored as potential TR agonists when the positive hit cut-off was defined at ≥10% efficacy, relative to maximal triiodothyronine (T₃) induction, and with only one of those compounds reaching ≥20% efficacy. One common class of compounds positive in the agonist assays were retinoids such as all-trans retinoic acid, which are likely acting via the retinoid-X receptor, the heterodimer partner with the TR. Five potential TR antagonists were identified, including the antiallergy drug tranilast and the anxiolytic drug SB 205384 but also some cytotoxic compounds like 5-fluorouracil. None of the inactive compounds were structurally related to T₃, nor had been reported elsewhere to be thyroid hormone disruptors, so false negatives were not detected. None of the low potency (>100µM) TR agonists resembled T₃ or T₄, thus these may not bind directly in the ligand-binding pocket of the receptor. For TR agonists, in the qHTS, a hit cut-off of ≥20% efficacy at 100 µM may avoid identification of positives with low or no physiological relevance. The miniaturized GH3.TRE-Luc assay offers a promising addition to the in vitro test battery for endocrine disruption, and given the low percentage of compounds testing positive, its high-throughput nature is an important advantage for future toxicological screening.

Sesamol suppresses cyclooxygenase-2 transcriptional activity in colon cancer cells and modifies intestinal polyp development in Apc (Min/+) mice

Excessive prostaglandin production by cyclooxygenase-2 in stromal and epithelial cells is a causative factor of colorectal carcinogenesis. Thus, compounds which inhibit cyclooxygenase-2 transcriptional activity in colon epithelial cells could be candidates for anti-carcinogenic agents. A cyclooxygenase-2 transcriptional activity in the human colon cancer cell line DLD-1 has been measured using a β-galactosidase reporter gene system. Using this system, we demonstrated that the decrease in basal cyclooxygenase-2 transcriptional activities at 100 µM sesamol, one of the lignans in sesame seeds, was 50%. Other compounds in sesame seeds such as sesamin, sesamolin, ferulic acid, and syringic acid did not exhibit significant suppression of cyclooxygenase-2 transcriptional activity at up to 100 µM. In a following experiment, 6-week-old male Min mice, Apc-deficient mice, were divided into a non-treated and 500 ppm sesamol groups. At the age of 15 weeks, it was found that treatment with sesamol decreased the number of polyps in the middle part of small intestine to 66.1% of the untreated value. Moreover, sesamol suppressed cyclooxygenase-2 and cytosolic prostaglandin E2 synthase mRNA in the polyp parts. The present findings may demonstrate the novel anti-carcinogenetic property of sesamol, and imply that agents that can suppress cyclooxygenase-2 expression may be useful cancer chemopreventive agents.

Inhibitory effects of azole-type fungicides on interleukin-17 gene expression via retinoic acid receptor-related orphan receptors α and γ

The retinoic acid receptor-related orphan receptors α and γ (RORα and RORγ), are key regulators of helper T (Th)17 cell differentiation, which is involved in the innate immune system and autoimmune disorders. However, it remains unclear whether environmental chemicals, including pesticides, have agonistic and/or antagonistic activity against RORα/γ. In this study, we investigated the RORα/γ activity of several azole-type fungicides, and the effects of these fungicides on the gene expression of interleukin (IL)-17, which mediates the function of Th17 cells. In the ROR-reporter gene assays, five azole-type fungicides (imibenconazole, triflumizole, hexaconazole, tetraconazole and imazalil) suppressed RORα- and/or RORγ-mediated transcriptional activity as did benzenesulphonamide T0901317, a ROR inverse agonist and a liver X receptor (LXR) agonist. In particular, imibenconazole, triflumizole and hexaconazole showed RORγ inverse agonistic activity at concentrations of 10(-6)M. However, unlike T0901317, these fungicides failed to show any LXRα/β agonistic activity. Next, five azole-type fungicides, showing ROR inverse agonist activity, were tested on IL-17 mRNA expression in mouse T lymphoma EL4 cells treated with phorbol myristate acetate and ionomycin. The quantitative RT-PCR analysis revealed that these fungicides suppressed the expression of IL-17 mRNA without effecting RORα and RORγ mRNA levels. In addition, the inhibitory effect of imibenconazole as well as that of T0901317 was absorbed in RORα/γ-knocked down EL4 cells. Taken together, these results suggest that some azole-type fungicides inhibit IL-17 production via RORα/γ. This also provides the first evidence that environmental chemicals can act as modulators of IL-17 expression in immune cells.

Modification at the Lipophilic Domain of RXR Agonists Differentially Influences Activation of RXR Heterodimers

RXR permissive heterodimers are reported to be activated differently depending upon the chemical structure of RXR agonists, but the relationship of agonist structure to differential heterodimer activation has not been explored in detail. In this study, we performed systematic conversion of the alkoxy side chain of 5a (6-[ethyl-(3-isopropoxy-4-isopropylphenyl)amino]nicotinic acid, NEt-3IP) and evaluated the RXR-, PPAR/RXR-, and LXR/RXR-agonist activities of the products. The cyclopropylmethoxy analogue (5c) showed similar RXR- and LXR/RXR-agonistic activities to the benzyloxy analogue (5i) and n-propoxy analogue (5k) but exhibited more potent PPAR/RXR-agonistic activity than 5i or 5k. Differential modulation of RXR heterodimer-activating ability by conversion of the alkoxy group located in the lipophilic domain of the RXR-agonist common structure is expected be a useful approach in the design of new RXR agonists for the treatment of hyperlipidemia or type 2 diabetes.

MicroRNA-196 represses Bach1 protein and hepatitis C virus gene expression in human hepatoma cells expressing hepatitis C viral proteins

Hepatitis C virus (HCV) directly induces oxidative stress and liver injury. Bach1, a basic leucine zipper mammalian transcriptional repressor, negatively regulates heme oxygenase 1 (HMOX1), a key cytoprotective enzyme that has antioxidant and anti-inflammatory activities. microRNAs (miRNAs) are small noncoding RNAs ( approximately 22 nt) that are important regulators of gene expression. Whether and how miRNAs regulate Bach1 or HCV are largely unknown. The aims of this study were to determine whether miR-196 regulates Bach1, HMOX1, and/or HCV gene expression. HCV replicon cell lines (Con1 and 9-13) of the Con1 isolate and J6/JFH1-based HCV cell culture system were used in this study. The effects of miR-196 mimic on Bach1, HMOX1, and HCV RNA, and protein levels were measured by way of quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting, respectively. The Dual Glo Luciferase Assay System was used to determine reporter activities. miR-196 mimic significantly down-regulated Bach1 and up-regulated HMOX1 gene expression and inhibited HCV expression. Dual luciferase reporter assays demonstrated that transfection of miR-196 mimic resulted in a significant decrease in Bach1 3'-untranslated region (UTR)-dependent luciferase activity but not in mutant Bach1 3'-UTR-dependent luciferase activity. Moreover, there was no detectable effect of mutant miR-196 on Bach1 3'-UTR-dependent luciferase activity.

CONCLUSION

miR-196 directly acts on the 3'-UTR of Bach1 messenger RNA and translationally represses the expression of this protein, and up-regulates HMOX1. miR-196 also inhibits HCV expression in HCV replicon cell lines (genotype 1b) and in J6/JFH1 (genotype 2a) HCV cell culture system. Thus, miR-196 plays a role in both HMOX1/Bach1 expression and the regulation of HCV expression in human hepatocytes. Overexpression of miR-196 holds promise as a potential novel strategy to prevent or ameliorate hepatitis C infection, and to protect against liver injury in chronic HCV infection.

Development of human cell biosensor system for genotoxicity detection based on DNA damage-induced gene expression

Background

Human exposure to genotoxic agents in the environment and everyday life represents a serious health threat. Fast and reliable assessment of genotoxicity of chemicals is of main importance in the fields of new chemicals and drug development as well as in environmental monitoring. The tumor suppressor gene p21, the major downstream target gene of activated p53 which is responsible for cell cycle arrest following DNA damage, has been shown to be specifically up-regulated by genotoxic carcinogens. The aim of our study was to develop a human cell-based biosensor system for simple and fast detection of genotoxic agents.

Methods

Metabolically active HepG2 human hepatoma cells were transfected with plasmid encoding Enhanced Green Fluorescent Protein (EGFP) under the control of the p21 promoter (p21HepG2GFP). DNA damage was induced by genotoxic agents with known mechanisms of action. The increase in fluorescence intensity, due to p21 mediated EGFP expression, was measured with a fluorescence microplate reader. The viability of treated cells was determined by the colorimetric MTS assay.

Results

The directly acting alkylating agent methylmethane sulphonate (MMS) showed significant increase in EGFP production after 48 h at 20 μg/mL. The indirectly acting carcinogen benzo(a)pyren (BaP) and the cross-linking agent cisplatin (CisPt) induced a dose- dependent increase in EGFP fluorescence, which was already significant at concentrations 0.13 μg/mL and 0.41 μg/mL, respectively. Vinblastine (VLB), a spindle poison that does not induce direct DNA damage, induced only a small increase in EGFP fluorescence intensity after 24 h at the lowest concentration (0.1 μg/mL), while exposure to higher concentrations was associated with significantly reduced cell viability.

Conclusions

The results of our study demonstrated that this novel assay based on the stably transformed cell line p21HepG2GFP can be used as a fast and simple biosensor system for detection of genetic damage caused by chemical agents.

Nuclear hormone receptor activity of polybrominated diphenyl ethers and their hydroxylated and methoxylated metabolites in transactivation assays using Chinese hamster ovary cells

BACKGROUND

An increasing number of studies are reporting the existence of polybrominated diphenyl ethers (PBDEs) and their hydroxylated (HO) and methoxylated (MeO) metabolites in the environment and in tissues from wildlife and humans.

OBJECTIVE

Our aim was to characterize and compare the agonistic and antagonistic activities of principle PBDE congeners and their HO and MeO metabolites against human nuclear hormone receptors.

METHODS

We tested the hormone receptor activities of estrogen receptor alpha (ERalpha), ERbeta, androgen receptor (AR), glucocorticoid receptor (GR), thyroid hormone receptor alpha(1) (TRalpha(1)), and TRbeta(1) against PBDE congeners BDEs 15, 28, 47, 85, 99, 100, 153, and 209, four para-HO-PBDEs, and four para-MeO-PBDEs by highly sensitive reporter gene assays using Chinese hamster ovary cells.

RESULTS

Of the 16 compounds tested, 6 and 2 showed agonistic activities in the ERalpha and ERbeta assays, respectively, and 6 and 6 showed antagonistic activities in these assays. 4'-HO-BDE-17 showed the most potent estrogenic activity via ERalpha/beta, and 4'-HO-BDE-49 showed the most potent anti estrogenic activity via ERalpha/beta. In the AR assay, 13 compounds showed antagonistic activity, with 4'-HO-BDE-17 in particular inhibiting AR-mediated transcriptional activity at low concentrations in the order of 10(-8) M. In the GR assay, seven compounds, including two HO-PBDEs and two MeO-PBDEs, showed weak antagonistic activity. In the TRalpha(1) and TRbeta(1) assays, only 4-HO-BDE-90 showed weak antagonistic activity.

CONCLUSIONS

Taken together, these results suggest that PBDEs and their metabolites might have multiple endocrine-disrupting effects via nuclear hormone receptors, and para-HO-PBDEs, in particular, possess more potent receptor activities compared with those of the parent PBDEs and corresponding para-MeO-PBDEs.

Oxidant stress stimulates expression of the human peroxiredoxin 6 gene by a transcriptional mechanism involving an antioxidant response element

Peroxiredoxin 6 (Prdx6) is a unique antioxidant enzyme that can reduce phospholipid and other hydroperoxides. A549 cells, a human lung-derived cell line, express both Prdx6 and Nrf2, a transcription factor that binds to antioxidant-response elements (AREs) and promotes expression of antioxidant genes. Treatment of A549 cells with 500 microM H(2)O(2) increased Prdx6 mRNA levels 2.5-fold, whereas treatment with 400 microM H(2)O(2) or 200 microM tert-butylhydroquinone (t-BHQ) triggered a corresponding 2.5-fold increase in reporter gene activity in A549 cells transfected with the pSEAP2:Basic vector (BD Bioscience), containing 1524 nucleotides of the human Prdx6 promoter region. Deletion of a consensus ARE sequence present between positions 357 and 349 before the start of transcription led to a striking decrease in both basal and H(2)O(2)- or t-BHQ-induced activation in A549 cells and H(2)O(2)-induced activation in primary rat alveolar type II cells. Cotransfection with Nrf2 stimulated the Prdx6 promoter in an ARE-dependent manner, whereas it was negatively regulated by Nrf3. siRNA targeting Nrf2 down-regulated reporter gene expression, whereas siRNA targeting the Nrf2 repressor, Keap1, up-regulated it. Binding of Nrf2 to the ARE sequence in chromatin was confirmed by PCR after chromatin immunoprecipitation. These data demonstrate that the ARE within the Prdx6 promoter is a key regulator of basal transcription of the Prdx6 gene and of its inducibility under conditions of oxidative stress.

Transfection of Primary Cultures of Rat Hepatocytes

Five different transfection reagents-calcium phosphate, TransFast™ Transfection Reagent, Superfect™ Transfection Reagent, Effectene™ Transfection Reagent, and Tfx™-20-were compared for their ability to effectively transfect primary cultures of male rat hepatocytes. Hepatocytes were isolated by the collagenase perfusion method and then cultured on Matrigel-coated plates for 24 h before transfection. The cells were transfected with either pGL3-Control or pGL3-Basic plasmids. The efficiency of transfection of each reagent was monitored using the dual luciferase reporter gene assay system. Superfect Transfection Reagent, Effectene Transfection Reagent and Tfx-20 were the most effective for the transfection of primary hepatocytes and gave comparable transfection efficiencies. Calcium phosphate was found to be the least effective transfection reagent and gave the most variable transfection results. Tfx-20 gave the least variable transfection results when different hepatocyte preparations were compared.

An in vitro approach to test the possible role of candidate factors in the transcriptional regulation of the RET proto-oncogene

Neural crest cells arise from the epithelium of the dorsal neural tube and migrate to various districts giving origin, among others, to sympathetic, parasympathetic, and enteric ganglia. It has been shown that the transcription factors HOX11L1, HOX11L2, MASH1, PHOX2A, and PHOX2B are all necessary, to various extents, to the correct development of the autonomic nervous system. To investigate their possible role in the transcriptional regulation of the RET proto-oncogene, a gene playing a crucial role in correct intestinal innervation, we undertook a specific in vitro experimental strategy. Two neuroblastoma cell lines (SK-N-MC and SK-N-BE) were cotransfected with each transcription factor expressing plasmids and sequential deletion constructs of the 5' c-RET flanking region cloned upstream of the Luciferase reporter gene. Here we show that HOX11L1 enhances the activity of the c-RET promoter in SK-N-MC cell line by stimulating a region between -166 bp and -35 bp. Gel shift assays performed with oligonucleotides spanning this promoter sequence showed a change of the SP1 interaction with its binding sites, consequent to transfection with HOX11L1. While HOX11L2 showed no effect in both the cell lines, we have observed PHOX2A, PHOX2B, and MASH1 triggering a reproducible increase in the Luciferase activity in SK-N-BE cell line. A sequence responsible of the PHOX2A-dependent activation has been identified, while PHOX2B seems to act indirectly, as no physical binding has been demonstrated on c-RET promoter.

Upregulation of vasopressin V1A receptor mRNA and protein in vascular smooth muscle cells following cyclosporin A treatment

1. The major side effects of the immunosuppressive drug cyclosporin A (CsA) are hypertension and nephrotoxicity. It is likely that both are caused by local vasoconstriction. 2. We have shown previously that 20 h treatment of rat vascular smooth muscle cells (VSMC) with therapeutically relevant CsA concentrations increased the cellular response to [Arg8]vasopressin (AVP) by increasing about 2 fold the number of vasopressin receptors. 3. Displacement experiments using a specific antagonist of the vasopressin V1A receptor (V1AR) showed that the vasopressin binding sites present in VSMC were exclusively receptors of the V1A subtype. 4. Receptor internalization studies revealed that CsA (10(-6) M) did not significantly alter AVP receptor trafficking. 5. V1AR mRNA was increased by CsA, as measured by quantitative polymerase chain reaction. Time-course studies indicated that the increase in mRNA preceded cell surface expression of the receptor, as measured by hormone binding. 6. A direct effect of CsA on the V1AR promoter was investigated using VSMC transfected with a V1AR promoter-luciferase reporter construct. Surprisingly, CsA did not increase, but rather slightly reduced V1AR promoter activity. This effect was independent of the cyclophilin-calcineurin pathway. 7. Measurement of V1AR mRNA decay in the presence of the transcription inhibitor actinomycin D revealed that CsA increased the half-life of V1AR mRNA about 2 fold. 8. In conclusion, CsA increased the response of VSMC to AVP by upregulating V1AR expression through stabilization of its mRNA. This could be a key mechanism in enhanced vascular responsiveness induced by CsA, causing both hypertension and, via renal vasoconstriction, reduced glomerular filtration.

Suppression by flavonoids of cyclooxygenase-2 promoter-dependent transcriptional activity in colon cancer cells: structure-activity relationship

Cyclooxygenase-2 (COX-2) plays an important role in carcinogenesis. Investigation of the suppressive action of twelve flavonoids of different chemical classes on the transcriptional activity of the COX-2 gene in human colon cancer DLD-1 cells using a reporter gene assay have revealed quercetin to be the most potent suppressor of COX-2 transcription (IC50 = 10.5 microM), while catechin and epicatechin showed weak activity (IC50 = 415.3 microM). Flavonoids have three heterocyclic rings as a common structure. A structure-activity study indicated that the number of hydroxyl groups on the B ring and an oxo group at the 4-position of the C ring are important in the suppression of COX-2 transcriptional activity. A low electron density of the oxygen atom in the hydroxyl group of the A ring was also important. Further examination of the role of the hydroxyl group in the A ring showed that bromination of resacetophenone to give 3,5-dibromo-2,4-dihydroxyacetophenone resulted in a 6.8-fold increase in potency for suppressing COX-2 promoter activity. These results provide a basis for the design of improved suppressors of COX-2 transcriptional activity.

Down-regulation of the expression of endothelial NO synthase is likely to contribute to glucocorticoid-mediated hypertension

Hypertension is a side effect of systemically administered glucocorticoids, but the underlying molecular mechanism remains poorly understood. Ingestion of dexamethasone by rats telemetrically instrumented increased blood pressure progressively over 7 days. Plasma concentrations of Na(+) and K(+) and urinary Na(+) and K(+) excretion remained constant, excluding a mineralocorticoid-mediated mechanism. Plasma NO(2)(-)/NO(3)(-) (the oxidation products of NO) decreased to 40%, and the expression of endothelial NO synthase (NOS III) was found down-regulated in the aorta and several other tissues of glucocorticoid-treated rats. The vasodilator response of resistance arterioles was tested by intravital microscopy in the mouse dorsal skinfold chamber model. Dexamethasone treatment significantly attenuated the relaxation to the endothelium-dependent vasodilator acetylcholine, but not to the endothelium-independent vasodilator S-nitroso-N-acetyl-D,L-penicillamine. Incubation of human umbilical vein endothelial cells, EA.hy 926 cells, or bovine aortic endothelial cells with several glucocorticoids reduced NOS III mRNA and protein expression to 60-70% of control, an effect that was prevented by the glucocorticoid receptor antagonist mifepristone. Glucocorticoids decreased NOS III mRNA stability and reduced the activity of the human NOS III promoter (3.5 kilobases) to approximately 70% by decreasing the binding activity of the essential transcription factor GATA. The expressional down-regulation of endothelial NOS III may contribute to the hypertension caused by glucocorticoids.